Growth, mortality, parasitism, and potential yields of two Priacanthus species in the South China Sea

Abstract

In the northern part of the South China Sea the ‘big‐eye’, Priacanthus tayenus, spawned once a year in June, had von Bertalanffy growth parameters of k = 0.8 and L∞= 30 cm, and a mean total annual instantaneous mortality of Z= 2.0, calculated from adjusted catch curves and a mean length equation. The natural mortality rate M= 1.4, fishing mortality rate F= 0.6, and the exploitation rate (E) was 0.27. The maximum potential yield, calculated using Marten's method, was 0.06 kg/recruit when F= 5.4. The fish were heavily parasitised by the protozoan Pleistophora priacanthicola.A second big‐eye, P. macracanthus, spawned twice a year in May‐June and September, had growth parameters of κ= 0.7 and L∞= 32, and population parameters of Z= 2.0, .F= 0.7, and E= 0.34. The maximum potential yield was 0.13 kg/recruit when F= 5.8.A marked reduction in fishing mortality occurred for both species between 1965 and 1966, coinciding with the onset of the Chinese Cultural Revolution. Our estimates of maximum potential yield correspond to fishing mortalities eight times estimated levels, though such heavy exploitation could risk recruitment failure.